I had a little bit of extra batter and buttercream, so I made these cupcakes to sample.
The lemon buttercream is made using lemon curd. Lemon curd is so delicious! I use it in a shortbread tart shell for lemon tarts, or injected into cupcakes, as I did here. It's also wonderful with cubed pound cake, berries, and whipped cream as a trifle.
1 cup (8 ounces) fresh squeezed lemon juice
8 ounces egg yolk (from about 10-12 eggs)
1 1/4 cups (8 ounces) sugar
pinch of kosher salt
1 1/2 Tablespoons lemon zest
Bring the lemon juice to a simmer in a medium pot.
Meanwhile, whisk together the yolks, sugar, and salt. When the lemon juice begins to bubble, being whisking some into the yolk, about 2 ounces at a time. Once the yolks are lemony and warm, pour them into the pot and cook on medium low heat, stirring constantly with a heat resistant spatula, until the curd has a thick, pudding-like consistency (about 165°).
Strain into the bowl of a stand mixer, discarding any bits that remain. Add the lemon zest and, with the paddle attachment, stir on low 5 minutes, until the curd has cooled to lukewarm.
Pour into a bowl, cover with plastic wrap flush on the surface of the curd, and refrigerate up to one week.